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Helene Marsh - One of the best experts on this subject based on the ideXlab platform.
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Dugong (Dugong dugon) movements and habitat use in a coral reef lagoonal ecosystem
Endangered Species Research, 2020Co-Authors: Christophe Cleguer, Claire Garrigue, Helene MarshAbstract:Little is known about how the Vulnerable Dugong Dugong dugon uses coral reef lagoons despite the importance of these habitats throughout much of its vast range. We used GPS satellite tracking systems to explore the space use of 12 Dugongs at 3 locations in the coral reef lagoons of the main island of New Caledonia in the southwest Pacific: Cap Goulvain, Ouano and Noumea. The movements of the tracked Dugongs varied among individuals and all except one animal undertook large-scale movements (>15 km; mean [±SE] 37.7 ± 5.2 km) from their capture location (maximum waterway distance range: 13.8 to 72.9 km). The straight-line distances between the furthest GPS locations during each animal’s tracking period ranged from 21.3 to 74.5 km. We identified areas used intensively by Dugongs in all 3 study areas, some of which were areas where seagrass presence has not been verified, or where Dugongs have not been observed during past aerial surveys. Dugongs spent most of their tracking time within the lagoons, with 99.4% of GPS locations found inside the barrier reef. Nonetheless, where the lagoon was narrow and confined, 3 tracked Dugongs used the fore reef shelf outside the barrier reef in the open ocean to commute between bays. Our findings can inform conservation and management initiatives in New Caledonia as well as other countries within the Dugong’s range which have similar habitat geomorphology but where Dugongs occur in numbers too low to be tracked and are considered Critically Endangered.
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compensating for geographic variation in detection probability with water depth improves abundance estimates of coastal marine megafauna
PLOS ONE, 2018Co-Authors: Rie Hagihara, R E Jones, S Sobtzick, Christophe Cleguer, Claire Garrigue, Helene MarshAbstract:The probability of an aquatic animal being available for detection is typically <1. Accounting for covariates that reduce the probability of detection is important for obtaining robust estimates of the population abundance and determining its status and trends. The Dugong (Dugong dugon) is a bottom-feeding marine mammal and a seagrass community specialist. We hypothesized that the probability of a Dugong being available for detection is dependent on water depth and that Dugongs spend more time underwater in deep-water seagrass habitats than in shallow-water seagrass habitats. We tested this hypothesis by quantifying the depth use of 28 wild Dugongs fitted with GPS satellite transmitters and time-depth recorders (TDRs) at three sites with distinct seagrass depth distributions: 1) open waters supporting extensive seagrass meadows to 40 m deep (Torres Strait, 6 Dugongs, 2015); 2) a protected bay (average water depth 6.8 m) with extensive shallow seagrass beds (Moreton Bay, 13 Dugongs, 2011 and 2012); and 3) a mixture of lagoon, coral and seagrass habitats to 60 m deep (New Caledonia, 9 Dugongs, 2013). The fitted instruments were used to measure the times the Dugongs spent in the experimentally determined detection zones under various environmental conditions. The estimated probability of detection was applied to aerial survey data previously collected at each location. In general, Dugongs were least available for detection in Torres Strait, and the population estimates increased 6-7 fold using depth-specific availability correction factors compared with earlier estimates that assumed homogeneous detection probability across water depth and location. Detection probabilities were higher in Moreton Bay and New Caledonia than Torres Strait because the water transparency in these two locations was much greater than in Torres Strait and the effect of correcting for depth-specific detection probability much less. The methodology has application to visual survey of coastal megafauna including surveys using Unmanned Aerial Vehicles.
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spatial mismatch between marine protected areas and Dugongs in new caledonia
Biological Conservation, 2015Co-Authors: Claire Garrigue, Christophe Cleguer, Alana Grech, Helene MarshAbstract:Marine protected areas (MPAs) are a powerful tool for conserving marine biodiversity when designed using ecological information and conservation goals and targets. Dugongs (Dugong dugon) were not an explicit target in the design of the network of MPAs in New Caledonia, despite being one of the region's World Heritage values. Our study retrospectively assessed the capacity of the New Caledonia MPA net- work to protect Dugongs from anthropogenic threats. We developed a spatially explicit model of Dugong distribution and relative density based on information collected from 10 years of aerial surveys. We quantified the amount of overlap between areas supporting high densities of Dugongs and MPAs. We found that most of the important Dugong habitats of New Caledonia had a low coverage of MPAs that pro- vide high levels of restriction on anthropogenic activities. We identified several important Dugong hab- itats along the west and the north-east coast that were not covered by MPAs and should be a priority for future management. The spatial mismatch between MPAs and Dugongs was likely caused by weaknesses in the planning process, including the: (1) lack of explicit conservation goals and targets; (2) omission of spatial information on species' distribution; (3) mismatch of spatial scales; (4) cost considerations; and (5) incorrect application of the IUCN protected area categories. We provide guidance on how these short- comings can be avoided for marine species of conservation concern in New Caledonia and other regions.
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using parallel regional and local scale initiatives to inform conservation management of rare wildlife a case study of the Dugong Dugong dugon in sabah malaysia
Endangered Species Research, 2010Co-Authors: Leela Rajamani, Helene MarshAbstract:Obtaining the information needed to inform management strategies for rare wildlife species at appropriate scales is costly and logistically demanding. Using coastal aerial surveys we obtained qualitative information on the distribution and abundance of the Dugong Dugong dugon at the geopolitical scale of the state of Sabah in east Malaysia. At a local scale, interview surveys and a monitoring program were carried out at 2 sites: Mantanani Island and Banggi Island. A total of 53 Dugongs were observed from the air, concentrated around Labuan Island — Brunei Bay and San- dakan Bay. The interview reports and monitoring program indicated that the residents of Mantanani Island and Banggi Island had local knowledge of the distribution and abundance of Dugongs and, thus, an ability to participate in monitoring at that scale. Dugong populations in Sabah are small and clumped, and urgently require management intervention at local scales in the regionally important habitats identified by the aerial surveys. This combination of regional- and local-scale initiatives has a more generic application in the monitoring of other rare species of wildlife.
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condition trends and predicted futures of Dugong populations in the great barrier reef world heritage area including an evaluation of the potential and cost effectiveness of indicators of the status of these populations
2010Co-Authors: Alana Grech, Helene MarshAbstract:The Dugong (Dugong dugon) is the only strictly marine herbivorous mammal and the only member of the family Dugongidae. Dugongs and the three species of manatee are the only living species in the order Sirenia; one of three orders of mammals considered at significant risk of extinction at the ordinal level (Purvis et al. 2000). Dugongs can live for about 70 years, and reach a maximum size of between 2 – 3 m. Female Dugongs have a minimum pre-reproductive period of between 6 – 17 yr (Marsh et al. 1984; Boyd et al. 1999; Kwan 2002) and a mean calving interval of between 2.4 – 7 yr. The age at first breeding and the time interval between calves is apparently dependent on the status of food supply (Boyd et al. 1999; Marsh and Kwan 2008). Dugongs are bottom feeders, and seagrasses are the most important component of their diet. Dugongs graze predominantly on intertidal and subtidal tropical and subtropical seagrass meadows, but are also known to feed on macro-invertebrates and algae. They feed on nine of the ten seagrass genera and on most of the species of seagrass that occur within their range (Green and Short 2003). Dugongs typically feed on several species of seagrass in mixed species seagrass meadows (Johnstone and Hudson 1981). The selection of seagrasses as food by Dugongs is influenced by multiple factors including fibre, nitrogen and starch content and biomass (Lanyon and Sanson 2006); but as pointed out by Aragones et al. (2006), the nutritional basis for food selection by Dugongs is poorly understood. Dugongs are found in the shallow, protected coastal waters of about 40 countries and territories in the tropical and subtropical Indian and Pacific Oceans. At a global scale, their distribution is characterised by relict populations separated by large areas where Dugongs are believed to be close to extinction or extinct locally (Marsh et al. 2002). A recent synthesis suggests that Dugongs are declining or locally extinct in at least a third of its range; of unknown status in nearly half; and possibly stable in the remainder (Marsh 2008). Dugongs are listed under the: IUCN Red List of Threatened Species as ‘Vulnerable’ to extinction; Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora 1973; and Appendix II of the Convention for Migratory Species of Wild Animals 1979.
Janet M. Lanyon - One of the best experts on this subject based on the ideXlab platform.
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Hematology of Dugongs (Dugong dugon) in southern Queensland
Veterinary Clinical Pathology, 2015Co-Authors: Lucy Woolford, Arthur Wong, Helen L. Sneath, Trevor Long, Susan P. Boyd, Janet M. LanyonAbstract:Background: Little is known of the hematology of the Dugong (Dugong dugon), a secretive and endangered coastal marine mammal. Objectives: This paper reports hematologic reference intervals (RI) for Dugongs and characterizes morphologic, cytochemical, and ultrastructural features of Dugong leukocytes. Methods: Blood was collected from live, apparently healthy Dugongs and analyzed using Cell-Dyn 3700 or Sysmex XT-2000iV hematology analyzers. Blood films were subjected to a series of cytochemical stains, and leukocyte structure was examined using transmission electron microscopy. Results: Reference intervals were established for 14 hematologic variables, total solids, and fibrinogen for 92 Dugongs. Significant differences in some variables were found for animal size class, sex, and pregnancy status, and between analyzers. Subadults had higher leukocyte and lymphocyte counts than adults. Males had higher total solids and fibrinogen than females. Pregnant females had higher HCT, MCV, and circulating nucleated RBC, and lower platelet counts than nonpregnant females. Lymphocytes were usually the predominant circulating leukocyte. Heterophil cytoplasmic granules were abundant, fine, round to ovoid, and intensely eosinophilic, and round to ovoid or rod-shaped, and variably electron dense in electron microscopy. Eosinophils contained larger round eosinophilic to orange cytoplasmic granules, which ultrastructurally were bicompartmental with a round eccentric electron-dense core. Cytochemical staining of Dugong heterophils suggests biochemical similarity to those of manatees and elephants, and for eosinophils, similarity to those of elephants, ruminants, and equids. Conclusions: Generation of hematologic RI and characterization of leukocyte morphology improves evaluation of Dugong health across this population and serves as a reference for other populations outside southern Queensland.
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serum biochemistry reference intervals of live wild Dugongs Dugong dugon from urban coastal australia
Veterinary Clinical Pathology, 2015Co-Authors: Janet M. Lanyon, Arthur Wong, Trevor Long, Lucy WoolfordAbstract:Background Little is known about the baseline clinical pathology of the Dugong (Dugong dugon), a vulnerable marine mammal found in tropical coastal marine systems. Objectives The purpose of the study was to collect and determine reference intervals (RI) for select serum biochemical variables for Dugongs, and to analyze differences between males and females and different age groups. Methods Reference intervals were established from 103 apparently healthy, wild-caught Dugongs for 31 analytes using a Beckman Coulter AU400 Automated Chemistry Analyzer and an Olympus AU680 Chemistry-Immuno Analyzer. Results Significant differences (P < .05) in some of the variables were found related to size class, sex, and pregnancy status. Adult Dugongs had higher serum sodium, potassium, bicarbonate, glucose, and l-lactate concentrations and higher anion gap, compared to sub-adults. Male Dugongs had higher triglyceride and l-lactate concentrations than females. Pregnant females displayed higher l-lactate levels compared to nonpregnant animals. Statistical differences in variables within the population contributed to better understanding of the physiologic differences between cohorts. Some serum biochemistry changes observed in this study here also potentially include some effects of pursuit on Dugongs (eg, higher l-lactate); however, as all Dugongs were subject to similar capture and handling, serum biochemistry RI should be considered as normal for captured Dugongs. Conclusions The serum biochemical RI documented here are considered representative of a population of healthy captured Dugongs. They provide a baseline for health surveillance of this and other Dugong populations.
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pathological findings in wild harvested Dugongs Dugong dugon of central torres strait australia
Diseases of Aquatic Organisms, 2015Co-Authors: Lucy Woolford, Craig E Franklin, T Whap, F Loban, Janet M. LanyonAbstract:The Dugong Dugong dugon is classified as Vulnerable to extinction but may be endangered in some regions. Cause of death in stranded Dugongs has not been determined in a large proportion of animals examined, with investigations hindered by limited information on Dugong health and diseases, and paucity of knowledge of common or endemic pathological findings. Here we describe pathological findings in harvested Dugongs from the relatively pristine area of central Torres Strait, and we characterise lesions attributable to drowning. Other recorded lesions were mild and predominated by host reaction to the presence of trematodes within the gastrointestinal tracts, liver and pancreas. Ascarid worm burdens were low in comparison to Dugongs from developed coastlines. Hepatocellular lipofuscin and ferritin pigmentation were commonly observed, more pronounced in livers of older animals and concurrent with periportal and bridging fibrosis. Lesions attributable to drowning included incomplete collapse of lungs, dorsal or diffuse pulmonary congestion, mild intra-alveolar haemorrhage and oedema, mild interstitial oedema and rupture of peripheral alveolar septae with acute myofibre fragmentation and degeneration. No accumulation of foam or aspiration of water or particulate matter was observed, suggesting that Dugongs 'dry drown'. Morphometric features of normal spleen are also presented. Characterisation of common pathological findings and those attributable to drowning in this species will aid in the interpretation of post mortem findings for the significant number of Dugongs found deceased along urbanised coastlines.
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Fine scale population structure of Dugongs (Dugong dugon) implies low gene flow along the southern Queensland coastline
Conservation Genetics, 2014Co-Authors: Jennifer M. Seddon, Damien Broderick, Jennifer R. Ovenden, Helen L. Sneath, Christine L. Dudgeon, Janet M. LanyonAbstract:Populations of marine mammals can show the signature of phylogeographical breaks and restricted connectivity despite the apparent lack of physical boundaries in the marine environment and their high dispersal abilities. Dugongs ( Dugong dugon ) do not appear to undertake regular migrations but may show localised movement related to water temperature or seagrass availability. Previous mitochondrial DNA studies suggested that despite a strong phylogeographic break in the Torres Strait, there is local panmixia in Australian waters. In this study, we conducted a comprehensive study of the four major Dugong populations in southern Queensland. We analysed genotypes of 1,293 Dugongs based on 24 microsatellite loci from the four major Dugong locations in the region (from south to north): Moreton Bay, Great Sandy Straits, Hervey Bay and Shoalwater Bay. Diversity levels were similar across locations (observed heterozygosity 0.48–0.52, allelic richness 4.3–4.5). There was low but significant population differentiation in southern Queensland (F_ST ranged from 0.005 to 0.040 and Jost’s D_EST ranged from 0.001 to 0.031 for microsatellite data). Bayesian clustering analysis implemented in STRUCTURE largely distinguished the southern Moreton Bay population from the three more northern populations. Twelve mitochondrial control region haplotypes identified from a subset of 182 samples confirmed significant population structuring (F_ST ranged from 0.16 to 0.28). These data suggested that the frequency and extent of Dugong movements are insufficient to disrupt the long-term existence of at least two breeding populations in southern Queensland.
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insulative capacity of the integument of the Dugong Dugong dugon thermal conductivity conductance and resistance measured by in vitro heat flux
Marine Biology, 2014Co-Authors: Patrick Horgan, David T Booth, Cassandra Nichols, Janet M. LanyonAbstract:Extant sirenians are restricted to warm waters, presumably due to their low metabolism and poor thermoregulatory capacity, including thin blubber. When subjected to winter waters, Florida manatees (Trichechus manatus latirostris) migrate to warm areas, but Dugongs (Dugong dugon) do not and instead live year-round in winter waters as cool as 15–18 °C. Dugongs appear to be more active than manatees and may have higher metabolic rates, but little is known about thermal energetics or the insulative properties of their integument. This study investigated the physical and thermal properties of whole samples of Dugong integument, i.e. epidermis, dermis and hypodermis (blubber) sampled from fresh Dugong carcasses collected from 2004 to 2012 in Moreton Bay (27.21°S, 153.25°E). Physico-chemical properties (thickness, density and lipid content) of each component tissue layer were measured. Thermal conductance (C) and conductivity (k) were measured for each tissue layer through in vitro temperature flux experiments within an insulated chamber. C and k were higher for dermis (25.7 ± 1.2 W m−2 K−1, 0.43 ± 0.02 W m−1 K−1, respectively, n = 21) than blubber (24.3 ± 2.4 W m−2 K−1, 0.31 ± 0.01 W m−1 K−1, n = 21), suggesting that blubber, with higher density and lipid content, affords better insulation. However, because the dermis contributes 65 % of integumentary thickness, both layers contribute significantly to insulation. The integument of Dugongs is a poorer insulator compared to many cold-water marine mammals, but the greater thickness of its dermal layer means that despite its relatively thin blubber, its integumentary insulation is similar to warm-water dolphins of similar body size.
Christophe Cleguer - One of the best experts on this subject based on the ideXlab platform.
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Dugong (Dugong dugon) movements and habitat use in a coral reef lagoonal ecosystem
Endangered Species Research, 2020Co-Authors: Christophe Cleguer, Claire Garrigue, Helene MarshAbstract:Little is known about how the Vulnerable Dugong Dugong dugon uses coral reef lagoons despite the importance of these habitats throughout much of its vast range. We used GPS satellite tracking systems to explore the space use of 12 Dugongs at 3 locations in the coral reef lagoons of the main island of New Caledonia in the southwest Pacific: Cap Goulvain, Ouano and Noumea. The movements of the tracked Dugongs varied among individuals and all except one animal undertook large-scale movements (>15 km; mean [±SE] 37.7 ± 5.2 km) from their capture location (maximum waterway distance range: 13.8 to 72.9 km). The straight-line distances between the furthest GPS locations during each animal’s tracking period ranged from 21.3 to 74.5 km. We identified areas used intensively by Dugongs in all 3 study areas, some of which were areas where seagrass presence has not been verified, or where Dugongs have not been observed during past aerial surveys. Dugongs spent most of their tracking time within the lagoons, with 99.4% of GPS locations found inside the barrier reef. Nonetheless, where the lagoon was narrow and confined, 3 tracked Dugongs used the fore reef shelf outside the barrier reef in the open ocean to commute between bays. Our findings can inform conservation and management initiatives in New Caledonia as well as other countries within the Dugong’s range which have similar habitat geomorphology but where Dugongs occur in numbers too low to be tracked and are considered Critically Endangered.
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compensating for geographic variation in detection probability with water depth improves abundance estimates of coastal marine megafauna
PLOS ONE, 2018Co-Authors: Rie Hagihara, R E Jones, S Sobtzick, Christophe Cleguer, Claire Garrigue, Helene MarshAbstract:The probability of an aquatic animal being available for detection is typically <1. Accounting for covariates that reduce the probability of detection is important for obtaining robust estimates of the population abundance and determining its status and trends. The Dugong (Dugong dugon) is a bottom-feeding marine mammal and a seagrass community specialist. We hypothesized that the probability of a Dugong being available for detection is dependent on water depth and that Dugongs spend more time underwater in deep-water seagrass habitats than in shallow-water seagrass habitats. We tested this hypothesis by quantifying the depth use of 28 wild Dugongs fitted with GPS satellite transmitters and time-depth recorders (TDRs) at three sites with distinct seagrass depth distributions: 1) open waters supporting extensive seagrass meadows to 40 m deep (Torres Strait, 6 Dugongs, 2015); 2) a protected bay (average water depth 6.8 m) with extensive shallow seagrass beds (Moreton Bay, 13 Dugongs, 2011 and 2012); and 3) a mixture of lagoon, coral and seagrass habitats to 60 m deep (New Caledonia, 9 Dugongs, 2013). The fitted instruments were used to measure the times the Dugongs spent in the experimentally determined detection zones under various environmental conditions. The estimated probability of detection was applied to aerial survey data previously collected at each location. In general, Dugongs were least available for detection in Torres Strait, and the population estimates increased 6-7 fold using depth-specific availability correction factors compared with earlier estimates that assumed homogeneous detection probability across water depth and location. Detection probabilities were higher in Moreton Bay and New Caledonia than Torres Strait because the water transparency in these two locations was much greater than in Torres Strait and the effect of correcting for depth-specific detection probability much less. The methodology has application to visual survey of coastal megafauna including surveys using Unmanned Aerial Vehicles.
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spatial mismatch between marine protected areas and Dugongs in new caledonia
Biological Conservation, 2015Co-Authors: Claire Garrigue, Christophe Cleguer, Alana Grech, Helene MarshAbstract:Marine protected areas (MPAs) are a powerful tool for conserving marine biodiversity when designed using ecological information and conservation goals and targets. Dugongs (Dugong dugon) were not an explicit target in the design of the network of MPAs in New Caledonia, despite being one of the region's World Heritage values. Our study retrospectively assessed the capacity of the New Caledonia MPA net- work to protect Dugongs from anthropogenic threats. We developed a spatially explicit model of Dugong distribution and relative density based on information collected from 10 years of aerial surveys. We quantified the amount of overlap between areas supporting high densities of Dugongs and MPAs. We found that most of the important Dugong habitats of New Caledonia had a low coverage of MPAs that pro- vide high levels of restriction on anthropogenic activities. We identified several important Dugong hab- itats along the west and the north-east coast that were not covered by MPAs and should be a priority for future management. The spatial mismatch between MPAs and Dugongs was likely caused by weaknesses in the planning process, including the: (1) lack of explicit conservation goals and targets; (2) omission of spatial information on species' distribution; (3) mismatch of spatial scales; (4) cost considerations; and (5) incorrect application of the IUCN protected area categories. We provide guidance on how these short- comings can be avoided for marine species of conservation concern in New Caledonia and other regions.
David Peel - One of the best experts on this subject based on the ideXlab platform.
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Unmanned Aerial Vehicles (UAVs) for surveying marine fauna: a Dugong case study
2016Co-Authors: Amanda Hodgson, Natalie Kelly, David PeelAbstract:Aerial surveys of marine mammals are routinely conducted to assess and monitor species ’ habitat use and population status. In Australia, Dugongs (Dugong dugon) are regularly surveyed and long-term datasets have formed the basis for defining habitat of high conservation value and risk assessments of human impacts. Unmanned aerial vehicles (UAVs) may facilitate more accurate, human-risk free, and cheaper aerial surveys. We undertook the first Australian UAV survey trial in Shark Bay, western Australia. We conducted seven flights of the ScanEagle UAV, mounted with a digital SLR camera payload. During each flight, ten transects covering a 1.3 km2 area frequently used by Dugongs, were flown at 500, 750 and 1000 ft. Image (photograph) capture was controlled via the Ground Control Station and the capture rate was scheduled to achieve a prescribed 10 % overlap between images along transect lines. Images were manually reviewed post hoc for animals and scored according to sun glitter, Beaufort Sea state and turbidity. We captured 6243 images, 627 containing Dugongs. We also identified whales, dolphins, turtles and a range of other fauna. Of all possible Dugong sightings, 95 % (CI = 90%, 98%) were subjectively classed as ‘certain’ (unmistakably Dugongs). Neither our Dugong sighting rate, nor our ability to identify Dugongs with certainty, were affected by UAV altitude. Turbidity was the only environmental variable significantly affecting the Dugong sighting rate. Our results suggest that UAV systems may not be limited by sea state conditions in the same manner a
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Unmanned aerial vehicles (UAVs) for surveying Marine Fauna: A Dugong case study
PLoS ONE, 2013Co-Authors: Amanda Hodgson, Natalie Kelly, David PeelAbstract:Aerial surveys of marine mammals are routinely conducted to assess and monitor species' habitat use and population status. In Australia, Dugongs (Dugong dugon) are regularly surveyed and long-term datasets have formed the basis for defining habitat of high conservation value and risk assessments of human impacts. Unmanned aerial vehicles (UAVs) may facilitate more accurate, human-risk free, and cheaper aerial surveys. We undertook the first Australian UAV survey trial in Shark Bay, western Australia. We conducted seven flights of the ScanEagle UAV, mounted with a digital SLR camera payload. During each flight, ten transects covering a 1.3 km(2) area frequently used by Dugongs, were flown at 500, 750 and 1000 ft. Image (photograph) capture was controlled via the Ground Control Station and the capture rate was scheduled to achieve a prescribed 10% overlap between images along transect lines. Images were manually reviewed post hoc for animals and scored according to sun glitter, Beaufort Sea state and turbidity. We captured 6243 images, 627 containing Dugongs. We also identified whales, dolphins, turtles and a range of other fauna. Of all possible Dugong sightings, 95% (CI = 90%, 98%) were subjectively classed as 'certain' (unmistakably Dugongs). Neither our Dugong sighting rate, nor our ability to identify Dugongs with certainty, were affected by UAV altitude. Turbidity was the only environmental variable significantly affecting the Dugong sighting rate. Our results suggest that UAV systems may not be limited by sea state conditions in the same manner as sightings from manned surveys. The overlap between images proved valuable for detecting animals that were masked by sun glitter in the corners of images, and identifying animals initially captured at awkward body angles. This initial trial of a basic camera system has successfully demonstrated that the ScanEagle UAV has great potential as a tool for marine mammal aerial surveys.
Amanda Hodgson - One of the best experts on this subject based on the ideXlab platform.
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Unmanned Aerial Vehicles (UAVs) for surveying marine fauna: a Dugong case study
2016Co-Authors: Amanda Hodgson, Natalie Kelly, David PeelAbstract:Aerial surveys of marine mammals are routinely conducted to assess and monitor species ’ habitat use and population status. In Australia, Dugongs (Dugong dugon) are regularly surveyed and long-term datasets have formed the basis for defining habitat of high conservation value and risk assessments of human impacts. Unmanned aerial vehicles (UAVs) may facilitate more accurate, human-risk free, and cheaper aerial surveys. We undertook the first Australian UAV survey trial in Shark Bay, western Australia. We conducted seven flights of the ScanEagle UAV, mounted with a digital SLR camera payload. During each flight, ten transects covering a 1.3 km2 area frequently used by Dugongs, were flown at 500, 750 and 1000 ft. Image (photograph) capture was controlled via the Ground Control Station and the capture rate was scheduled to achieve a prescribed 10 % overlap between images along transect lines. Images were manually reviewed post hoc for animals and scored according to sun glitter, Beaufort Sea state and turbidity. We captured 6243 images, 627 containing Dugongs. We also identified whales, dolphins, turtles and a range of other fauna. Of all possible Dugong sightings, 95 % (CI = 90%, 98%) were subjectively classed as ‘certain’ (unmistakably Dugongs). Neither our Dugong sighting rate, nor our ability to identify Dugongs with certainty, were affected by UAV altitude. Turbidity was the only environmental variable significantly affecting the Dugong sighting rate. Our results suggest that UAV systems may not be limited by sea state conditions in the same manner a
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2015Co-Authors: Amanda J. Hodgsonab, Amanda HodgsonAbstract:Shark Bay is believed to be home to more than 10 % of the world’s Dugongs, (Dugong dugon), (Marsh et al., 2002; Gales et al., 2004), and the importance of Shark Bay as a significant habitat for Dugongs was one of the reasons for its World Heritage listing. Shark Bay arguably offers the best opportunity to conserve Dugongs in the world because it: a) is isolated from urban development; b) has a low level of Indigenous hunting and c) occurs within a Marine Park and World Heritage Area. The four systematic surveys of Shark Bay conducted to date suggest that the population is consistently above 10,000 Dugongs. Ningaloo Reef and Exmouth Gulf also support significant Dugong populations that are to be interconnected with Shark Bay. The last survey conducted in the Shark Bay / Ningaloo / Exmouth region showed a dramatic decline in Dugong abundance in association with a significant increase in Shark Bay, suggesting that Dugongs had moved southward following the loss of seagrass during a cyclone event in the northern region. This finding was evidence of a link between the Shark Bay and Ningaloo-Exmouth Dugong populations, which therefore, cannot be managed in isolation. Aims of this projec
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Unmanned aerial vehicles (UAVs) for surveying Marine Fauna: A Dugong case study
PLoS ONE, 2013Co-Authors: Amanda Hodgson, Natalie Kelly, David PeelAbstract:Aerial surveys of marine mammals are routinely conducted to assess and monitor species' habitat use and population status. In Australia, Dugongs (Dugong dugon) are regularly surveyed and long-term datasets have formed the basis for defining habitat of high conservation value and risk assessments of human impacts. Unmanned aerial vehicles (UAVs) may facilitate more accurate, human-risk free, and cheaper aerial surveys. We undertook the first Australian UAV survey trial in Shark Bay, western Australia. We conducted seven flights of the ScanEagle UAV, mounted with a digital SLR camera payload. During each flight, ten transects covering a 1.3 km(2) area frequently used by Dugongs, were flown at 500, 750 and 1000 ft. Image (photograph) capture was controlled via the Ground Control Station and the capture rate was scheduled to achieve a prescribed 10% overlap between images along transect lines. Images were manually reviewed post hoc for animals and scored according to sun glitter, Beaufort Sea state and turbidity. We captured 6243 images, 627 containing Dugongs. We also identified whales, dolphins, turtles and a range of other fauna. Of all possible Dugong sightings, 95% (CI = 90%, 98%) were subjectively classed as 'certain' (unmistakably Dugongs). Neither our Dugong sighting rate, nor our ability to identify Dugongs with certainty, were affected by UAV altitude. Turbidity was the only environmental variable significantly affecting the Dugong sighting rate. Our results suggest that UAV systems may not be limited by sea state conditions in the same manner as sightings from manned surveys. The overlap between images proved valuable for detecting animals that were masked by sun glitter in the corners of images, and identifying animals initially captured at awkward body angles. This initial trial of a basic camera system has successfully demonstrated that the ScanEagle UAV has great potential as a tool for marine mammal aerial surveys.
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occurrence and conservation of the Dugong sirenia Dugongidae in new south wales
Allen S. Marsh H. and Hodgson A. ORCID: 0000-0002-9479-3018 (2004) Occurrence and conservation of the dugong (Sirenia: Dugongidae) in New South Wales., 2004Co-Authors: Simon Allen, Helene Marsh, Amanda HodgsonAbstract:Recent sightings of Dugongs well beyond the southern limit of their accepted range (~27°S) on the Australian east coast prompted a review of past records of Dugongs and their current conservation status in New South Wales. While archaeological analyses have identified bones of Dugong dugon in Aboriginal middens at Botany Bay (~34°S) and colonial records indicate stranded animals as far south as Tathra (~36.5°S), there were no verified sightings of live individuals in NSW waters for some years; however, five separate sightings of individuals and pairs were documented in the austral summer of 2002/03 in estuaries on the NSW central coast (~32-33.5°S). It is suggested that conditions such as warm sea temperatures and low rainfall (promoting seagrass growth) may be facilitating explorative ranging south by Dugongs. The IUCN lists Dugongs as ‘vulnerable’ at a global scale and they are also classified ‘vulnerable’ under the Threatened Species Conservation Act NSW 1995, yet they are not routinely considered in risk assessments for inshore development in this State. Threatening processes such as shark meshing persist. The importance of considering Dugongs in future impact assessments for inshore marine and estuarine developments is emphasized.
